Example output:

% perf list
...
  arith.fpu_div
       [Divide operations executed]
  arith.fpu_div_active
       [Cycles when divider is busy executing divide operations]

Signed-off-by: Andi Kleen <redacted>
Signed-off-by: Sukadev Bhattiprolu <redacted>
Acked-by: Jiri Olsa <redacted>
Acked-by: Ingo Molnar <mingo@kernel.org>
---

Changelog
	- Delete a redundant free()

Changelog[v14]
	- [Jiri Olsa] Fail, rather than continue if strdup() returns NULL;
	  remove unnecessary __maybe_unused.
---
 tools/perf/util/pmu.c | 83 +++++++++++++++++++++++++++++++++++++++++----------
 tools/perf/util/pmu.h |  1 +
 2 files changed, 68 insertions(+), 16 deletions(-)

diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
index c842886..af1a612 100644
--- a/tools/perf/util/pmu.c
+++ b/tools/perf/util/pmu.c

@@ -222,7 +222,7 @@ static int perf_pmu__parse_snapshot(struct perf_pmu_alias *alias,
 }
 
 static int __perf_pmu__new_alias(struct list_head *list, char *dir, char *name,
-				 char *desc __maybe_unused, char *val)
+				 char *desc, char *val)
 {
 	struct perf_pmu_alias *alias;
 	int ret;

@@ -255,6 +255,8 @@ static int __perf_pmu__new_alias(struct list_head *list, char *dir, char *name,
 		perf_pmu__parse_snapshot(alias, dir, name);
 	}
 
+	alias->desc = desc ? strdup(desc) : NULL;
+
 	list_add_tail(&alias->list, list);
 
 	return 0;

@@ -1044,11 +1046,42 @@ static char *format_alias_or(char *buf, int len, struct perf_pmu *pmu,
 	return buf;
 }
 
-static int cmp_string(const void *a, const void *b)
+struct pair {
+	char *name;
+	char *desc;
+};
+
+static int cmp_pair(const void *a, const void *b)
+{
+	const struct pair *as = a;
+	const struct pair *bs = b;
+
+	/* Put extra events last */
+	if (!!as->desc != !!bs->desc)
+		return !!as->desc - !!bs->desc;
+	return strcmp(as->name, bs->name);
+}
+
+static void wordwrap(char *s, int start, int max, int corr)
 {
-	const char * const *as = a;
-	const char * const *bs = b;
-	return strcmp(*as, *bs);
+	int column = start;
+	int n;
+
+	while (*s) {
+		int wlen = strcspn(s, " \t");
+
+		if (column + wlen >= max && column > start) {
+			printf("\n%*s", start, "");
+			column = start + corr;
+		}
+		n = printf("%s%.*s", column > start ? " " : "", wlen, s);
+		if (n <= 0)
+			break;
+		s += wlen;
+		column += n;
+		while (isspace(*s))
+			s++;
+	}
 }
 
 void print_pmu_events(const char *event_glob, bool name_only)

@@ -1058,7 +1091,9 @@ void print_pmu_events(const char *event_glob, bool name_only)
 	char buf[1024];
 	int printed = 0;
 	int len, j;
-	char **aliases;
+	struct pair *aliases;
+	int numdesc = 0;
+	int columns = 78;
 
 	pmu = NULL;
 	len = 0;

@@ -1068,14 +1103,15 @@ void print_pmu_events(const char *event_glob, bool name_only)
 		if (pmu->selectable)
 			len++;
 	}
-	aliases = zalloc(sizeof(char *) * len);
+	aliases = zalloc(sizeof(struct pair) * len);
 	if (!aliases)
 		goto out_enomem;
 	pmu = NULL;
 	j = 0;
 	while ((pmu = perf_pmu__scan(pmu)) != NULL) {
 		list_for_each_entry(alias, &pmu->aliases, list) {
-			char *name = format_alias(buf, sizeof(buf), pmu, alias);
+			char *name = alias->desc ? alias->name :
+				format_alias(buf, sizeof(buf), pmu, alias);
 			bool is_cpu = !strcmp(pmu->name, "cpu");
 
 			if (event_glob != NULL &&

@@ -1084,12 +1120,19 @@ void print_pmu_events(const char *event_glob, bool name_only)
 						       event_glob))))
 				continue;
 
-			if (is_cpu && !name_only)
+			if (is_cpu && !name_only && !alias->desc)
 				name = format_alias_or(buf, sizeof(buf), pmu, alias);
 
-			aliases[j] = strdup(name);
-			if (aliases[j] == NULL)
+			aliases[j].name = name;
+			if (is_cpu && !name_only && !alias->desc)
+				aliases[j].name = format_alias_or(buf,
+								  sizeof(buf),
+								  pmu, alias);
+			aliases[j].name = strdup(aliases[j].name);
+			if (!aliases[j].name)
 				goto out_enomem;
+
+			aliases[j].desc = alias->desc;
 			j++;
 		}
 		if (pmu->selectable &&

@@ -1097,25 +1140,33 @@ void print_pmu_events(const char *event_glob, bool name_only)
 			char *s;
 			if (asprintf(&s, "%s//", pmu->name) < 0)
 				goto out_enomem;
-			aliases[j] = s;
+			aliases[j].name = s;
 			j++;
 		}
 	}
 	len = j;
-	qsort(aliases, len, sizeof(char *), cmp_string);
+	qsort(aliases, len, sizeof(struct pair), cmp_pair);
 	for (j = 0; j < len; j++) {
 		if (name_only) {
-			printf("%s ", aliases[j]);
+			printf("%s ", aliases[j].name);
 			continue;
 		}
-		printf("  %-50s [Kernel PMU event]\n", aliases[j]);
+		if (aliases[j].desc) {
+			if (numdesc++ == 0)
+				printf("\n");
+			printf("  %-50s\n", aliases[j].name);
+			printf("%*s", 8, "[");
+			wordwrap(aliases[j].desc, 8, columns, 0);
+			printf("]\n");
+		} else
+			printf("  %-50s [Kernel PMU event]\n", aliases[j].name);
 		printed++;
 	}
 	if (printed && pager_in_use())
 		printf("\n");
 out_free:
 	for (j = 0; j < len; j++)
-		zfree(&aliases[j]);
+		zfree(&aliases[j].name);
 	zfree(&aliases);
 	return;
 

diff --git a/tools/perf/util/pmu.h b/tools/perf/util/pmu.h
index 5d7e844..11bda57 100644
--- a/tools/perf/util/pmu.h
+++ b/tools/perf/util/pmu.h

@@ -38,6 +38,7 @@ struct perf_pmu_info {
 
 struct perf_pmu_alias {
 	char *name;
+	char *desc;
 	struct list_head terms; /* HEAD struct parse_events_term -> list */
 	struct list_head list;  /* ELEM */
 	char unit[UNIT_MAX_LEN+1];

-- 
1.8.3.1